Geersen, Jacob , Behrmann, Jan Hinrich , Völker, David, Krastel, Sebastian , Ranero, Cesar R., Diaz-Naveas, Juan and Weinrebe, Reimer Wilhelm (2011) Active tectonics of the South Chilean marine fore arc (35°S - 40°S). Tectonics, 30 . TC3006. DOI 10.1029/2010TC002777.

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Abstract

The South Chilean marine fore arc (35°S–40°S) is separated into four tectonic
segments, Concepción North, Concepción South, Nahuelbuta, and Tolten (from north to
south). These are each characterized by their individual tectonic geomorphology and
reflect different ways of mechanical and kinematic interaction of the convergent Nazca and
South American plates. Splay faults that cut through continental framework rock are
seismically imaged in both Concepción segments and the Tolten Segment. Additionally,
the Concepción South Segment exhibits prominent upper plate normal faults. Normal
faults apparently relate to uplift caused by sediment underthrusting at depth. This has led to
oversteepening and gravitational collapse of the marine fore arc. There is also evidence for
sediment underthrusting and basal accretion to the overriding plate in the Tolten Segment.
There, uplift of the continental slope has created a landward inclined seafloor over a
latitudinal distance of 50 km. In the Nahuelbuta Segment transpressive upper plate faults,
aligned oblique to the direction of plate motion, control the seafloor morphology. Based on
a unique acoustic data set including >90% of bathymetric coverage of the continental
slope we are able to reveal an along‐strike heterogeneity of a complexly deformed marine
fore arc which had escaped attention in previous studies that only considered the structure
along transects normal to the plate margin.

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